U.S. Pat. No. 6,468,222 to Mault et al. discloses an indirect calorimeter having a flow pathway, through which respired gases pass, a flow meter, and a gas component sensor. Oxygen consumption can be determined for a subject at rest, allowing their resting metabolic rate to be determined.
Ultrasonic transducers can be used to measure flow rates of gases within a flow pathway, for example as described in U.S. Pat. Nos. 5,419,326, 5,503,151, 5,645,071, and 5,647,370 to Hamoncourt, and U.S. Pat. No. 5,796,009 to Delsing.
Oxygen sensors provide a signal correlated with oxygen partial pressure within respired gases. Fluorescent oxygen sensors can be used to determine the oxygen concentration in respired gases, for example as described by Colvin in U.S. Pat. Nos. 6,344,360, 6,330,464, 6,304,766, 5,917,605, 5,910,661, 5,894,351, and 5,517,313.
Respiratory analyzers are described by Brugnoli in U.S. Pat. Nos. 6,206,837, 4,658,832, and 4,631,966. These devices use a turbine flow meter that may be subject to errors due to inertial effects. Indirect calorimeters are also described in U.S. Pat. Nos. 5,060,656, 5,117,674, and 5,363,857, to Howard. These devices use a sampling method to analyze respired gases, which adds to weight, expense, and complexity.
Other respiratory analyzers are described in U.S. patent application Nos. 2003/0065273, 2003/0023182, 2003/0105407, 2003/0028120, 2003/0065274, and 2003/0065275, to Mault and co-inventors.
All U.S. patents and patent applications referred to in this application are incorporated herein by reference. U.S. Provisional Applications Nos. 60/400,265 (filed Aug. 1, 2002), 60/405,850 (filed Aug. 23, 2002), 60/412,155 (filed Sep. 19, 2002), 60/413,505 (filed Sep. 25, 2002), 60/429,252 (filed Nov. 26, 2002), and 60/445,595 (filed Nov. 26, 2002) are incorporated herein by reference.